Explore the vast range of titles available.

According to the requirement of microwave frequency measurement, a microwave frequency measurement system is designed based on six-port device. The system includes a microwave power divider, delay lines, a microwave phase discriminator, detectors, a signal source, a oscilloscope and so on. The microwave phase discriminator is realized by six-port circuit. The determination method of delay line length is explained, the phase calculation method of six–port phase discriminator is deduced, and the relationship between frequency, phase difference and delay line is given. According to the method, a microwave frequency measurement system is built to measure the sine wave signal with frequency of 2GHz to 8GHz. The best relative error of the measurement is 1.9×10 −3 . The results show that the six-port device can be applied to the microwave frequency measurement system. In the future, the research on wide-band and high accuracy frequency measurement technology will be further carried out.

Instantaneous frequency measurement devices are designated for very fast measurements of the current frequency value of microwave signals, even if they are very short in the time domain. Fast measurements of frequency temporary values may be based on the evaluation of the phase difference of signal propagating through the microwave transmission lines with unequal, but known, lengths. This paper presents the principle of determination of temporary values of the microwave signal frequency using the digitalized signals and the binary value of them eventually. In the purpose of increase the frequency discrimination resolution, additional tracks with lines with a larger length are proposed. For the system with elements with analytical model transmission characteristics it is typical that bands of ambiguity of frequency measurement occurs. To tackle this problem in addition to 4 x 4 Butler matrix implementation the method of using combination sine and cosine signals is proposed.

To measure the micro-displacement reliably with high precision, a single-ended eddy current sensor based on temperature compensation was studied in detail. At first, the principle of the eddy current sensor was introduced, and the manufacturing method of the probe was given. The overall design plan for the processing circuit was induced by analyzing the characteristics of the probe output signal. The variation in the probe output signal was converted to pulses with different widths, and then it was introduced to the digital phase discriminator along with a reference signal. The output from the digital phase discriminator was processed by a low-pass filter to obtain the DC component. At last, the signal was amplified and compensated to reduce the influence of temperature. The selection criteria of the frequency of the exciting signal and the design of the signal conditioning circuit were described in detail, as well as the design of the temperature-compensating circuit based on the digital potentiometer with an embedded temperature sensor. Finally, an experimental setup was constructed to test the sensor, and the results were given. The results show that nonlinearity exists in the single-ended eddy current sensor with a large range. When the range is 500 μm, the resolution can reach 46 nm, and the repeatability error is ±0.70% FR. Within the temperature range from +2 °C to +58 °C, the voltage fluctuation in the sensor is reduced to 44 mV after temperature compensation compared to the value of 586 mV before compensation. The proposed plan is verified to be feasible, and the measuring range, precision, and target material should be considered in real-world applications.

Locating active radars in real environmental conditions is a very important and complex task. The efficiency of the direction finding (DF) of ground-based radars and other microwave emitters using unmanned aerial vehicles (UAV) is dependent on the parameters of applied devices for angle location of microwave emitters, and on the construction and modes of operation of the observed transmitting antenna systems. An additional factor having the influence on DF of the radar, when are used systems installed on the UAV, is the rotation of the antenna of a radar. The accuracy of estimation of direction of any microwave transmitter is determined by the terrain properties that surround the transmitter and the objects reflecting microwave signals. The exemplary shapes of the radar antenna patterns and the associated relationships with the probability of remotely detecting the radar and determining its bearings are described. The simulated patterns of the signals received at an emitter-locating device mounted on a UAV and the expected results of a monopulse DF based on these signals are presented. The novelty of this work is the analysis of the DF efficiency of radars in conditions where intense multi-path phenomena appear, and for various amplitudes and phases of the direct signal and multi-path signals that reach the UAV when assuming that so-called simple signals and linear frequency modulation (LFM) signals are transmitted by the radar. The primary focus is on multi-path phenomenon, which can make it difficult, but not entirely impossible, to detect activity and location of radar with a low-flying small UAV and using only monopulse techniques, that is, when only a single pulse emitted by a radar must be sufficient to DF of this radar. Direction of arrival (DOA) algorithms of signals in dense signal environment were not presented in the work, but relevant suggestions were made for the design of such algorithms.

Instantaneous frequency measurement devices are useful for conducting extremely fast measurements of the current frequency value of microwave signals, even if their duration is extremely short. This paper presents the principle of determination of temporary values of the microwave signal phase and frequency using interferometer techniques, based on passive microwave components. Additionally, the structures and results of measurements of two novel versions of integrated microwave correlators for microwave frequency discriminators, made on a single printed circuit board, are shown. Three Wilkinson-type, single-stage power dividers, and two rat-race hybrids create the developed correlators. The developed devices were designed to work over a wide frequency range, i.e., of 1.6–3.1 GHz, and can be used to monitor Wi-Fi devices as well as pulse and CW radar systems operating in the S band. They can also be applied in passive radars and active Doppler radars. The view of the printed circuits boards and results of measurements are presented. Recommendations for improving the accuracy of measurement are proposed.

We have developed algorithms for a logic device with enhanced functionality and a variety of structural implementations to compare the frequency and phase of the input pulse signals of frequency phase-locked loops.

The conventional phase deviation discriminator used in the decision feedback loop for carrier synchronization of APSK signal requires symbol decision for every constellation symbol. When the number of constellation symbols used for coherent integration becomes larger, the complexity would increase greatly. To solve this problem, this work proposes an improved phase deviation discriminator based on symbol decisions. It firstly executes doubling frequency on the APSK signal to reduce the modulation order and eliminate the modulation phase of the received signal. Then, it rotates the constellation clockwise and selects the constellation symbols that on the X-axis to execute coherent integration and phase deviation extraction. Compared to the conventional discriminator in the decision feedback loop, the proposed discriminator can reduce the symbol decision times and steps. Therefore, when a large number of constellation symbols are used for coherent integration, it can reduce the computational complexity significantly. Moreover, with a large number of constellation symbols, the proposed discriminator achieves better BER and RMSE performance than other existing feedback loops.

Methods are developed for the numerical determination of the angular acceleration and the error in the angular velocity of a synchrophase electric drive. The proposed methods are based on an analysis of the mutual order of reference-frequency pulses and feedback pulses in saturation regimes of a logic comparator.

A Concept of a Passive Radar with Quadrature Microwave Phase Discriminators Passive radar does not have its own emitter. It uses so-called signals of opportunity emitted by non-cooperative illuminators. During the detection of reflected signals, a direct signal from a non-cooperative emitter is used as the reference signal. Detection of electromagnetic echoes is, in present day radars, performed by finding the maximum of the cross ambiguity function. This function is based on the multiplication of the received signal and the reference signal. Detection of echoes by means of a quadrature microwave phase discriminator QMPD was proposed in the work as an alternative solution for ambiguity function evaluation. This discriminator carries out vectorial summing of the received and the reference signals. The summing operations in QMPD are carried out with the aid of microwave elements and without the use of expensive digital signal processors. Definitions of the phase and phase difference of the so-called simple signals and noise signals were described. A proposal of a passive radar equipped with several independent quadrature microwave phase discriminators was presented. Ideas of algorithms of object detection and of the distance-to-object estimation designed for this radar have been also sketched.

This paper introduces the composition and basic principle of phase locked frequency circuit, analysis of the dynamic characteristics of the loop, and the method to determine the parameters of phase locked loop circuit. The experimental results show that using the phase lock loop circuit designed by this method can be accurate and stable frequency trigger signals needed, as well as realize the synchronous and equal interval sampling, and the whole cycle voltage uniform subdivision. Meantime, it reduced the design difficulty, and has very strong applicability.